Elasticity Imaging is a known class of techniques for the estimation of mechanical properties of materials. In addition to diagnosis by palpation, methods have been proposed for elasticity imaging for biomechanics for measuring mechanical properties in vivo in a non invasive, non destructive manner.
Examples of the use of elasticity imaging methods for biomechanical applications include the use of Magnetic Resonance Elastography (MRE) for the determination of brain and liver tissue viscoelastic properties in vivo and comparison between in vivo and post-mortem brain properties, the use of MRE for the measurement of skeletal muscle contraction and muscle stiffness changes with aging, the use of Transient Elastography to assess skeletal muscle stiffness during contraction, or the use of Supersonic Shear Imaging (SSI) for the measurement of shear wave dispersion curves for characterization of soft tissue viscoelasticity.
Indentation is also a widely used material testing method that allows measuring the Load-Displacement curve. Analytical solutions are possible in the case of penetration of axisymetric indenters in an elastic half space. It is possible to derive the Young's modulus of the tested material, for example, by estimation using a complex iterative procedure and calibration process. While indentation is commonly used for materials such as polymers and metallic samples, the application of such an experimental approach is limited in in vivo contexts, due to the intrinsic limitations of indentation such as the need to apply forces externally or using invasive mechanisms.
Conventional quantitative mechanical testing methods are generally performed externally and, in operation, consist of using an actuator (e.g., a piston) that imposes a controlled force on the subject tissue. The mechanical response of the tissue is measured subsequently, allowing an estimate of the mechanical properties of the tested sample. Since the actuator is in contact with the subject tissue, such methods are limited to external testing. Presently, internal testing methods can be performed invasively.